Integrated circuits are made by forming on a substrate, such as a silicon wafer, layers of conductive material that are separated by layers of a dielectric material. Vias may be etched through the dielectric layers, then filled with a conducting material to electrically connect the separated conductive layers.
A commonly used dielectric material is silicon dioxide. Although a thermally stable and mechanically strong material, silicon dioxide has a relatively high dielectric constant. Consequently, as described in U.S. Pat. No. 5,886,410 and copending application Ser. No. 899,133 (filed Jul. 24, 1997), each assigned to this application's assignee, certain materials--such as various organic polymers--that have a relatively low dielectric constant may be used as a dielectric material in place of silicon dioxide. When such materials are used in place of those with a higher dielectric constant, RC delay may be reduced, which can enable a higher speed device.
This application describes an improved process for making an integrated circuit that uses a polymer based dielectric as an insulation layer formed between conductive layers.